1. Technical Field
The present invention relates to a recording medium transport device that transports a recording medium, and a recording device including the recording medium transport device.
2. Related Art
In a recording device that is represented by a printer, there is a case in which such a configuration is employed that a transport material, that is, a recording medium that is represented by a sheet of recording paper is transported using a transport belt. However, there is a case in which an accumulated material that originates from the recording medium, such as paper dust and fibers, and ink, attaches to the transport belt, and when the accumulated material and ink are transferred onto the recording medium, a reduction in the recording quality occurs. In particular, in the case of double-sided recording, ink, paper dust, and the like directly attach to the recording surface at the time of back-side recording, so that the recording quality is certainly reduced.
In addition, in the configuration in which the sheet of recording paper is transported using the transport belt, there is also a case in which the sheet of recording paper is attracted to the transport belt by electrostatic adsorption in order to prevent the sheet of recording paper from floating above the transport belt. In this case, paper dust, ink, and the like are more liable to attach to the transport belt, and for example, when ink attaches to the transport belt, there is a possibility that the electrical resistivity of the belt surface is reduced, and the transport belt cannot be charged appropriately.
In order to solve such problems, as an example of the related art, a device has been proposed that includes means for cleaning a transport belt as discussed in JP-A-2004-130721. An ink jet recording device that is discussed in JP-A-2004-130721 includes a cleaning blade. The cleaning blade comes into contact with the transport belt and wipes off ink that has attached to the belt surface.
As means for cleaning the transport belt that is provided in the recording device, in the related art, another configuration, for example, is employed in which a material that has accumulated on the belt surface is wiped off by an ink absorber in addition to the configuration in which the belt surface is wiped by the cleaning blade as described above.
Generally, a transport belt has a configuration of being spanned across a plurality of rotating bodies, and is driven. Here, there is a possibility that the transport belt moves in a belt width direction that is a thrust direction of the rotating bodies and is skewed, which causes a reduction in the recording quality. Therefore, in order to regulate such movement of the transport belt, as discussed in JP-A-2000-284635, there is a case in which projections that are called beads are provided on both edges of the inner surface of the belt, and both ends of the rotating body that the transport belt is spanned across are formed into a tapered shape, and the movement of the belt in the width direction is regulated by causing the beads to come into contact with the tapered portion.
In addition, it is necessary that looseness of the transport belt be regulated when the blade comes into contact with the belt surface because the cleaning blade comes into contact with the belt surface to wipe the belt surface. Therefore, it is desirable that the cleaning blade comes into contact with the belt surface at a position at which a certain configuration member exists on the inner surface of the belt, for example, at a position at which the rotating body exists.
Here, when the tapered portion that regulates the beads on the inner surface of the belt is provided on both ends of the rotating body, it is difficult to fix the position of the belt surface in this portion, and there is a possibility that the transport belt may break due to the movement of the beads onto the tapered portion, so that it is desirable that a configuration is employed in which the belt surface at the bead position is slightly sloped. Thus, in such a position, the cleaning blade is not practical, that is, the cleaning blade does not come into contact with the belt surface, and ink is not wiped off by the blade in the areas of both edges of the belt.
FIG. 4 is a cross-sectional view that indicates the axial end (axial end on one side) of the rotating body and the beads on the inner surface of the transport belt, and in FIG. 4, a transport belt 101, and a rotating body 103 that the transport belt 101 spans are illustrated. In FIG. 4, instead of the configuration in which the axial end of the rotating body 103 is formed into a tapered shape, a configuration is illustrated in which a skew regulation collar 104 that includes a taper 104a and regulates skew of the transport belt is used. Here, among the beads that are provided at both edges of the inner surface of the transport belt 101, beads 102 on one edge are illustrated. In the transport belt 101, skew is regulated by regulating movement in the right direction of FIG. 4 of the beads 102 using the taper 104a. On the other edge of the transport belt 101, the movement in the left direction of FIG. 4 of beads, which are not illustrated, is regulated.
It is difficult to fix the belt surface position in an area B outside the rotating body 103 in the transport belt 101, and there is a possibility that the transport belt 101 may become broken due to the movement of the beads 102 onto the taper 104a, so that a configuration may be employed in which the belt surface becomes slightly sloped at the position of the bead 102. In addition, there is a case in which the edge of the belt surface is slightly raised due to thermal contraction of the member depending on the configuration of the transport belt. Thus, in the area B, there is a case in which the cleaning blade is not practical or a case in which it is desirable that the cleaning blade does not come into contact with the belt surface.
In addition, in the case of the movement of the beads 102 onto the taper 104a, when the transport belt 101 comes into contact with the cleaning blade, there is a possibility that the transport belt 101 may become damaged. Thus, for that reason, it is desirable that the cleaning width of the transport belt 101 that is wiped by the cleaning blade is smaller than an area A of the rotating body 103.
For the above-described reason, when the width of the transport belt 101 is denoted as W6, the width of an area with which the transport belt 101 comes into contact in the rotating body 103 is denoted as W5, and the cleaning width of the transport belt 101 that is wiped by the cleaning blade is denoted as W3, it is desirable that “W6>W5>W3” is satisfied. The width W5 of the rotating body 103 indicates the width of an area with which the transport belt 101 comes into contact, and does not include the width of the skew regulation collar 104 and the width of the taper 104a. 
In addition, when the maximum paper width is denoted as W1, and the width (length) of an area in which the charging roller charges the transport belt 101 is denoted as W2, it is desirable that “W2>W1” is satisfied from the viewpoint of sufficient electrostatic adsorption. In addition, it is desirable that the cleaning width W3 of the transport belt 101 that is wiped by the cleaning blade is larger than the width W2 of the area in which the charging roller charges the transport belt 101 so that ink that has attached to the belt surface does not adversely affect charging of the belt by the charging roller. From the above-described viewpoint, it is desirable that “W6>W5>W3>W2>W1” is satisfied in the relationship between the above-described dimensions.
In the relationship between the above-described dimensions, the cleaning width W3 of the transport belt 101 that is wiped by the cleaning blade is smaller than the belt width W6, but when the belt surface is wiped by the cleaning blade, the wiped-off ink and accumulated material escape from both ends of the blade to the outside, that is, the ink and material are not wiped off, and the accumulated ink and material come into contact with and attach to an ink jet head, so that there is a possibility that the accumulated ink and material adversely affect ink discharge. Such a technological problem has not been considered in the related arts.